Plating the inside of a gas tank
A discussion started in 2004 but continuing through 20172004
Q. I am repairing an old motorcycle, the gas tank is rusted on the inside. I can buy a kit to clean the inside, and apply a liquid that cures into a plastic. I would rather plate the inside with tin, or lead. I can use an old battery terminal, or a roll of solder for an anode . The inside of the tank will be the cathode. I don't know what to use for an electrolyte. If solder is used for an anode will the individual element with the lower number on the galvanic scale be the one that plates out onto the cathode, the solder, being an alloy?
True Story , I sand blasted a brake drum , cast iron , and wanted to warm it up in my oven before spray painting it. Well, its a gas oven,and produces water vapor which flash rusted my freshly sandblasted part! I went down into the Basement , and dunked the brake drum into an acid solution that I previously used to De scale My tankless hot water heater ( copper tubes ). Much to my amazement, The brake drum became copper plated without a power source! I think Iron is lower than copper on the galvanic scale, if that had anything to do with it. Could you describe in layman's terms What happened?
3rd Question, some parts on my motorcycle are plated with a dark color I can only describe as Olive Drab- Almost Black. I need to know what this is called so when I talk to a plater,so I can ask them if they plate such a finish .Paul W [last name deleted for privacy by Editor]
Hobbyist - Old Bridge , New Jersey, USA
A. Please apply that liquid that you know about to plastic coat your tank, Paul. There are many reasons it's not practical to plate the tank.
Yes, if you dissolve an alloy like solder, the more noble component metal will plate out preferentially. You can predict the plate-out ratio from the Nernst Equation, but the short answer is that the plating will usually be nearly 100% the more noble metal.
Another True Story is that, in times that were less environmentally sensitive, scrap metal (like scrapped cars) would be placed into streams, downstream of copper processing facilities, to "plate out" the dissolved copper as you've described. You are correct that copper is more noble than iron and will spontaneously plate out onto iron. Although all explanations are simplifications, you can think of it this way: copper is better at holding onto electrons than iron is, so positively charged ions of copper will grab electrons from the iron, thus reducing the copper ions to copper atoms, and thus oxidizing the iron atoms to positively charged iron ions. So an atom of iron dissolves and replaces the atom of copper in solution. Immersion plating like this is very limited in thickness because as soon as there is a coating of copper, the underlying iron can no longer dissolve so no more copper will be replaced by it.
3rd answer: The parts that you describe are probably zinc plated or cadmium plated with an olive-drab chromate conversion coating. Yes, to answer your question, olive drab is the correct term.
Ted Mooney, P.E.
Pine Beach, New Jersey
Striving to live "Aloha"
A. Most likely the solution that plated your brake drum was ferric chloride, with a large quantity of copper dissolved in it. When you add a chunk of steel or iron to it you create a weak electric charge, which bonds the copper to the iron (I've used this trick myself on some show knives, oxidized the copper blue with ammonia afterward).Marc Banks
- Elizabeth City, North Carolina
August 5, 2012 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
Q. I want to galvanize the interior of my fuel tank. I just finished an electrolysis Rust removal and now I want to Galvanize it.
I have a piece of zinc.
For rust removal I have a positive charge steel as the sacrificial anode and Negative charged the tank. It took 36 hours to do and is very clean.
Now to Galvanize I fill the tank with water and sodium carbonate solution. Then I need to attach the positive to the tank and negative to the zinc.
Is that correct?
Let run until a galvanized coat is uniform throughout the tank?
- Monroe Virginia USA
A. Hi, Chester.
You seem to be talking about electroplating, not galvanizing. The tank (the cathode) remains attached to the negative for electroplating, and the zinc (the anode) is attached to the positive. Sodium carbonate is probably sufficiently alkaline to hold zinc in solution and thus allow electroplating in theory. But there is much more to successful electroplating than that, so I don't think you'll meet with success soon, if at all. I would strongly suggest that you practice on something else and see for yourself what you are up against, rather than ruining something that you have worked on so hard already. Best of luck.
Ted Mooney, P.E.
Pine Beach, New Jersey
Striving to live "Aloha"
October 5, 2013 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
Q. Dear Sirs,
I have a question for you.
I have a rusty gas tank of a motorcycle. I thought it would be good solution, the first to take off the rust so it will perform electrolysis solution of sodium bicarbonate (300 g in 17 l of water) and iron bar (+) inside of tank and tank (-). And when I derust it to copper plate it. The simple question is HOW?
My wish is to protect the tank so that it does not rust again.
- Belgrade, Serija
October 9, 2013
A. An easier solution would be to use a tank sealer like "Gold Standard Tank Sealer" or one of the many others widely available. You'll find that and many other options if you simply type 'sealing rusty tank interior' into google. Sadly, it's a common problem when restoring motorcycles.Fauna Tester
- Seattle, Washington, USA
October 10, 2013
A. If you spend a lot of time and money, you have about a 1% chance of doing a good enough job electroplating the inside a gas tank.
There are several companies who will properly hot dip galvanize the inside of gas tank for a reasonable price, and it will then last longer than the rest of the bike.
Check on the internet.
Jeffrey Holmes, CEF
Spartanburg, South Carolina
October 23, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
Q. I restore antique and classic motorcycles and since spares are non-existent I was wondering if there is some way to coat the gas tank from the inside. There are no leaks and if you could do something like a zinc coat from.the inside to extend their lifespans?Hugh Donnelly
Restorer - Lonavla Maharashtra India
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